Recently, much public attention has been focused on the production of tamper-resistant and tamper-evident packaging, particularly in the packaging of pharmaceuticals, cosmetics, and food. Tamper-evident packaging alerts the consumer that the package has been tampered with and thus warns of the potential for danger if the product is used. Many regulations have been enacted in an attempt to ensure that any tampering with certain products will indeed be evident.
A particularly popular packaging method for pharmaceuticals and cosmetics is involves the encasing of a container in a thin polymeric film. Typically this process comprises shrinking a film balloon onto the container through the application of any or all of heat, pressure, and vacuum; having shrunk to encase the container, the film can seal and protect the encased components. Encasing films are easily and inexpensively applied to containers and, depending on the film employed, can impart airtight, watertight, aseptic or other desirable properties to the container.
A shortcoming of containers encased in polymeric film is that the film can be quite easily removed from the container and replaced with a second film; thus one tampering with the container can remove the outer film, tamper with the contents of the container, and encase the container with a new film that is indistinguishable from the original to the consumer. Therefore a tamper-evident container encased in a thin film must provide indicia of tampering responsive to removal of the film from the container. This problem has been addressed in a number of different ways. For example, the film itself may comprise multiple layers which respond to rupture or some other disturbance by displaying indicia of tampering. See, e.g., U.S. Pat. No. 4,876,123 to Rivera et al.; U.S. Pat. No. 4,246,307 to Trautwein; U.S. Pat. No. 4,652,473 to Han. Others have disclosed packaging in which the encasing wrap lifts ink from the container upon its removal, thereby indicating tampering. See, e,g., U.S. Pat. No. 4,718,553 to Adamoli et al.; U.S. Pat. No. 4,972,953 to Friedman et al. Each of these methods can be rather expensive, so researchers are continually investigating new tamper-evident products and methods.